Strong Players Compare Candidates
Good quote from C. Hesse in his new, fun book The Joys of Chess (publisher: New in Chess), when summarizing A. de Groot's finding from the latter's famous (but not fun - more like a PhD thesis!) book Thought and Choice in Chess:
"Weaker players often follow their positional intuition and latch on to a specific move, check whether it makes sense or is reasonable and then play it it these points do check out. The thought process of the strong player, on the other hand, is aimed at proving that a move he has his eye on is in fact the best move."
This is very true. In administering 40+ years of de Groot exercises, I have found that inexperienced and weaker players rarely compare the positions that can occur after various candidate moves, assuming "best" sequences for each. Strong players, on the other hand, do these types of comparisons quite frequently. de Groot therefore calls the final step in these strong players' thought process "Striving for Proof".
The best candidate move you have found so far is your "King of the Hill" (KOTH). Suppose you are in an "analytical" position (one with meaningful checks, captures, and/or threats), and think move A is your KOTH. That means that if your opponent can reply to A with move B and you can counter with move C (assuming best moves and analyzing to quiescence), that the position C* is the best position you can get.
If you see another candidate X and anticipate the move sequence XYZ, then you want to compare position Z* to position C* to determine if Z* is a more desirable position for you. If so, then X replaces A as your KOTH (leading candidate move).
For example, in the following position...
...suppose the KOTH is 14...Qd6 threatening what Charles Hertan calls the "sneaky pin" move 15...Qg3+. Then after analyzing it, rather than just playing it if I think it is good, I might consider 14...Bxf2+ and see what happens after 15.Kxf2 Ne5 (not that this is quiescent!) to see if I like that better than what I anticipate will happen after 14...Qd6. This is nothing more than implementing "When you see a good move, don't play it. You are trying to find the best move you can, given the time constraints, so look for a better one." Note: If you find that a move wins easily and you're 100% sure, then it is almost never cost effective to look for a better one that wins "more easily".